(1) Field of the Invention
The present invention relates to an aparatus and a method for correction of a deviation of an imaging sensor of a digital camera which may be produced by a slight oscillation of the human hand in taking a photograph using the digital camera.
(2) Description of the Related Art
Recently, the rapid growth of digital cameras for business uses as well as for personal uses has been experienced. Developments of digital cameras having a small size and a light weight with low cost will be increased. With the developments of such digital cameras, attention will be focused on correction of a deviation of a digital camera caused by a slight oscillation of the human hand when taking a photograph with the digital camera.
If an imaging sensor of the digital camera deviates from a reference position due to the oscillation of the operator, a dim image will be reproduced by the digital camera. If the deviation of the imaging sensor is not corrected, it is difficult for the digital camera to provide good quality of a reproduced image. Therefore, there is a demand for a digital camera which is capable of automatically correcting a deviation of the imaging sensor which may be produced by a slight oscillation of the operator who takes a photograph with the digital camera.
In the fields of video cameras, techniques for correction of an image deviation of the video camera are known. For example, Japanese Laid-Open Patent Application No.64-78581 discloses a video camera deviation correcting device. This deviation correcting device includes a frame memory which stores an image signal. An image deviation caused by a camera deviation is detected from a difference in image data between two frames in a sequence of continuously processed image frames. When an image deviation is detected, the image data is processed with the frame memory by controlling the read/write timing of the frame memory so as to correct the image deviation.
In the device of the above publication, an acceleration sensor is provided to detect a camera motion. However, there is provided no moving mechanism which moves the imaging sensor based on the detected motion, so as to cancel the camera deviation having caused the image deviation.
Japanese Laid-Open Patent Application No. 2-103023 discloses a video camera deviation correcting device. The deviation correcting device includes horizontal and vertical line sensors which detect an image deviation caused by a camera deviation. Such an image deviation is detected from a difference in image data between two frames in a sequence of continuously processed image frames. When an image deviation is detected, the imaging sensor is moved on a plane perpendicular to the optical axis of the video camera lens by a moving mechanism so as to correct the image deviation.
Japanese Laid-Open Patent Application No. 6-46322 discloses an imaging apparatus having a deviation correcting function. The deviation correcting function of the imaging apparatus is applied to a video camera. A camera motion is detected by a vibration sensor. When a camera motion is detected, the imaging sensor is moved on a plane perpendicular to the optical axis of the video camera lens by a moving mechanism such that the center of the imaging sensor is aligned with the optical axis of the video camera lens.
The conventional techniques of the above publications are applied to the video cameras in which a sequence of image frames is continuously acquired and processed. However, it is very difficult to directly apply the video camera techniques to digital cameras in which a single frame of image data is acquired in an image acquisition time. In the case of digital cameras, it is necessary to correct a deviation of the imaging sensor of the digital camera within an image acquisition time for a single frame, in order to eliminate the degradation of quality of a reproduced image due to a slight oscillation of the operator.
Further, in the conventional techniques of the above publications, there is no teaching about how to detect the magnitude and the direction of an imaging sensor deviation with a required level of accuracy, and how to move the imaging sensor based on the detection result in an effective manner so as to cancel the imaging sensor deviation. It is desirable to provide such new techniques for digital cameras, in order to incorporate therein the functions to effectively correct a deviation of the imaging sensor and to reliably prevent the degradation of quality of a reproduced image due to a slight oscillation of the operator in taking a photograph with the digital camera.
An object of the present invention is to provide a novel and useful deviation correcting apparatus and method in which the above-described problems are eliminated.
Another object of the present invention is to provide a digital camera deviation correcting apparatus which reliably prevents the degradation of quality of a reproduced image of the digital camera due to a slight oscillation of the operator by correcting a deviation of the imaging sensor of the digital camera in an effective manner through an accurate detection of the imaging sensor deviation and a controlled movement of the imaging sensor based on the detection result.
Still another object of the present invention is to provide a digital camera deviation correcting method which reliably prevents the degradation of quality of a reproduced image of the digital camera due to a slight oscillation of the operator by correcting a deviation of the imaging sensor of the digital camera in an effective manner through an accurate detection of the imaging sensor deviation and a controlled movement of the imaging sensor based on the detection result.
The above-mentioned objects of the present invention are achieved by an apparatus for correcting a deviation of an imaging sensor of a digital camera in which an image of an object or a scene is formed on an image plane of the imaging sensor so that the imaging sensor outputs an image signal, which comprises: a rotation detecting unit which detects a quantity of rotation of the digital camera causing a deviation of the imaging sensor from a reference position to occur; a positional angle calculating unit which calculates a change of a positional angle of the imaging sensor based on the rotation quantity detected by the rotation detecting unit; a target vector calculating unit which calculates a target vector based on the positional angle change calculated by the positional angle calculating unit, the target vector describing a magnitude and a direction of an inverse movement of the imaging sensor needed to reach the reference position and cancel the deviation; and a movement control unit which controls movement of the imaging sensor based on the target vector calculated by the target vector calculating unit, so that the imaging sensor is moved back to the reference position thus correcting the deviation, wherein the calculation of the target vector and the movement of the imaging sensor are executed within an image acquisition time for a single frame of the image signal.
The above-mentioned objects of the present invention are achieved by a method of correcting a deviation of an imaging sensor of a digital camera in which an image of an object or a scene is formed on an image plane of the imaging sensor so that the imaging sensor outputs an image signal, comprising the steps of: detecting a quantity of rotation of the digital camera causing a deviation of the imaging sensor from a reference position to occur; calculating a change of a positional angle of the imaging sensor based on the detected rotation quantity; calculating a target vector based on the calculated positional angle change, the target vector describing a magnitude and a direction of an inverse movement of the imaging sensor needed to reach the reference position and cancel the deviation; and controlling movement of the imaging sensor based on the calculated target vector, so that the imaging sensor is moved back to the reference position thus correcting the deviation, wherein the calculation of the target vector and the movement of the imaging sensor are executed within an image acquisition time for a single frame of the image signal.
In the digital camera deviation correcting apparatus and method of the present invention, a quantity of rotation and/or a quantity of translation of the digital camera, causing a deviation of the imaging sensor from the reference position to occur, is detected by a rotation detecting unit and/or a translation detecting unit. A change of the positional angle of the imaging sensor is calculated based on the detected rotation quantity. A change of the quantity of translation of the imaging sensor is calculated based on the detected translation quantity. A target vector is calculated based on the calculated positional angle change and the calculated translation quantity change, the target vector describing a magnitude and a direction of an inverse movement of the imaging sensor needed to reach the reference position and cancel the deviation. Movement of the imaging sensor is controlled based on the calculated target vector, so that the imaging sensor is moved back to the reference position thus correcting the deviation. The calculation of the target vector and the movement of the imaging sensor are executed within an image acquisition time for a single frame of the image signal. It is possible for the digital camera incorporating the principles of the present invention to provide good quality of a reproduced image as the degradation of quality of a reproduced image due to a slight oscillation of the operator is effectively prevented. It is possible that the apparatus and the method of the present invention effectively corrects a deviation of the imaging sensor of the digital camera through an accurate detection of the imaging sensor deviation and a controlled movement of the imaging sensor based on the detection result.